Black Band Disease

Black band disease is characterized by a front of black, gooey material (mostly algae) behind which is denuded skeleton and in front of which is healthy tissue. The denuded skeleton is rapidly coated with many species of algae, including the black gooey mats characteristic of the black bands. It affects hard corals mostly, but also some soft corals, including gorgonians and Sinularia spp.

Current scientific studies indicate that several organisms cause this disease. While a particular species of cyanobacteria, Phormidium corallyticum, has been identified with this condition (see Ruetzler and Santavy, 1983), other species of cyanobacteria and filamentous algae are often present (P. Dustan, pers. comm.), sometimes in the complete absence of Phormidium. Also, many bacteria and microorganisms have been isolated from the bands, and these may either be directly involved in the tissue destruction or simply opportunistically consuming damaged tissue, other microorganisms, or cyanobacteria.

Treatment: Siphon the black front away using small diameter airline hose with a rigid airline tip. A teasing needle can be used to lift the black mat and separate it from the coral skeleton with the siphon close behind to catch the debris. The coral can be removed from the display tank and placed in the reservoir without illumination for about a week to allow the tissue a chance to begin healing without competing with new algae growth. Be sure that the coral receives adequate water movement if it is placed in the reservoir. If it is not possible to remove the coral from the display tank, be sure to siphon the band away as described and, if the band returns, apply small quantities of antibiotics such as

Chloramphenicol or Erythromycin directly on the affected area, as described in the treatment of "brown jelly". Freshwater dips also described for treating "brown jelly" kill cyanobacteria as well, and are an effective treatment. If the affected coral takes food, feeding it (sparingly) chopped shrimp or fish will assist healing.

Blackened Areas on Soft Coral

Soft corals may exhibit black, necrotic areas on branches, particularly Sinularia spp. and Caribbean photosynthetic gorgonians, especially Eunicea spp. This occurs when tissue has suffocated in shipment or when it has been attacked by a microorganism and died. Stinging from other corals can also cause this in gorgonians.

Treatment: Generally it is best just to direct a strong current stream over the coral and allow the necrotic areas to fall off on their own. Usually they do not spread. If they appear to be spreading despite good water flow, then it may be necessary to cut off the affected branches with a sharp scissors. When gorgonians lose tissue and the skeleton is exposed, it is a good site for attachment and growth of algae. If the exposed skeleton is only about half a centimeter or less, the tissue usually grows back rapidly before algae can grow. Larger gaps than this may make it necessary to cut the branch off. It is best to wait and allow the gorgonian a chance to heal to determine if cutting will be necessary. If algae grows on the skeleton and the tissue seems unable to grow there, the branch should be cut as close as possible to living tissue of the main colony. The free branch, if substantial, may then be transplanted in the aquarium after the algae is scraped off its base.

Gorgonian burned by Catalaphyllia. Note blackened necrotic tissue. S.W. Michael.

Aquarium SkeletonClam Excurrent Siphon

A second excurrent siphon has formed between the normal inhalent and exhalent siphons in this Tridacna derasa. It probably is the result of an injury that healed without closing up. J. Sprung.

Hole in the Mantle of Tridacnid Clams

Sometimes a tridacnid clam will develop a hole in the center of the mantle, between the inhalent and exhalent siphons. The wound can be fatal, but usually it spontaneously heals, leaving no scar. Sometimes a scar remains or, as in the photo, a second exhalent siphon forms. The causes of a hole developing in the mantle include physical injury, infection (bacterial or protozoan), and light damage. A tridacnid clam located less than eight inches from a metal halide bulb can suffer a burn that causes a hole to open in the mantle. Most metal halide bulbs have a focused ring or "hot spot" of light that can be observed by holding one's hand a few inches below the bulb. The high intensity of heat and light from this ring can burn clams and corals if they are near it. This is not a problem when the bulbs are located more than eight inches above the aquarium. If a clam develops a hole in the mantle, move it to a new location and observe it to make sure it is not being attacked. The wound should heal within a few days.

Broken Hinge in Tridacnid Clams

On rare occasions a tridacnid clam will suffer a break in the brown protein material joining the two shells. If this occurs, re-align the shells and affix a rubber band loosely around them to hold the hinge position while still allowing the shells to part enough for the mantle to extend and receive light. The clam will secrete a new hinge within about two weeks.

Diseases Echinodorus

Chapter Eleven

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  • georgina
    What Causes Black Band Disease?
    3 years ago

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